The present invention relates generally to the use of Mobile Internet Protocol (xe2x80x9cIPxe2x80x9d) systems, methods, and protocols in PCS systems to provide seamless mobility across multiple PCS data networks and IP networks.
With the proliferation of wireless cellular devices, an increasing need has arisen for a methodology and system to provide seamless mobile access to the Internet via existing personal communication services (xe2x80x9cPCSxe2x80x9d) networks. To meet this need, the wireless access system must support high-speed packet data transmissions and also internetwork with the Internet backbone efficiently. While emerging PCS technologies, such as CDMA2000 and Wideband CDMA (WCDMA), define packet data transmission over the air interface, these systems do not present a flexible architecture for connecting a wireless access system to the Internet backbone which is also suitable for general mobile IP interconnectivity.
FIG. 1 is an illustration of a conventional cellular system network 10. The network 10 includes a mobile switching center (xe2x80x9cMSCxe2x80x9d) 12 connected to one or more base station controllers (xe2x80x9cBSCxe2x80x9d) 14. Each BSC 14 controls one or more base stations (xe2x80x9cBSxe2x80x9d) 16 which provide wireless communication links to various mobile stations (xe2x80x9cMSxe2x80x9d) 18. The MSC 12 interfaces to a public switched telephone network (xe2x80x9cPSTNxe2x80x9d) 20 for routing the voice calls and to a separate signaling system 22 which provides signaling functionality used for PCS mobility management. Such a conventional cellular system provides Internet access through voiceband modems in the mobile stations which connect to an Internet access server interfaced to the MSC 12, either directly or via the PSTN 20. Alternatively, an interworking function (IWF) 24 interfaced directly to the MSC can support the interworking of protocols between the air interface and the Internet.
Although conventional cellular systems provide adequate data and voice service in some circumstances, this network configuration suffers from several deficiencies. In particular, the connection model is based on dialup modems where the IWF 24 acts as a server which provides a point-to-point connection to the MS 18 and assigns a temporary IP address to the MS that is valid only during the session. However, when an MS 18 changes its point of attachment with the Internet, a new session must be established and a new temporary address assigned to the MS 18. Thus, as the MS moves across different subnets, packet delivery to the MS is based on the temporary IP address and not the static IP address of the MS. This prevents the maintenance of an Internet session as the MS changes its point of attachment to the system. Because of the temporary address assignment to the MS in a visiting system, the MS can not act as a server. Further, SINCE the MS does not have a static IP address, datagrams cannot be delivered to the MS until the MS has independently established a Point-to-Point Protocol (xe2x80x9cPPPxe2x80x9d) session and the host attempting to send data knows the MS=s temporary IP address.
Other systems for providing wireless Internet access, such as cellular digital packet data (xe2x80x9cCDPDxe2x80x9d) and GSM packet radio service (xe2x80x9cGPRSxe2x80x9d), define specialized network protocols for packet-based wireless access techniques. However, CDPD network subsystems and mobility management designs are tightly coupled to a specific set of underlying lower layer protocols and are thus unsuitable for use with a wide variety of lower layer communications facilities. GPRS implementations maintain a strict separation between the radio subsystem and the network subsystem and rely on GSM mobility application protocol (MAP). In addition, to interwork with legacy networks, such as X.25, GPRS requires a complex layering of protocols. Thus, GPRS is also unsuitable for efficient implementation of Mobile IP functionality using various existing and emerging PCS systems.
Accordingly, it is an object of the present invention to provide a protocol and mobility management design for wireless Internet communication which can easily operate in conjunction with emerging and existing PCS technologies.
It is a further object of the invention to supply a protocol and system which provide seamless IP mobility across multiple PCS and IP networks while permitting any PCS air interface technology to be used.
According to the invention, a mobile IP architecture and methodology combine existing PCS structures with a separate IP network subsystem which employs Mobile IP techniques such that the mobile host has a static IP address but can still seamlessly change its point of attachment to the Internet.
In particular, each BSC in a PCS network is configured to route voice traffic to the MSC. Data traffic is routed to a separate gateway router which is connected between at least one BSC and the Internet. Mobile IP interconnectivity is provided on two levelsxe2x80x94globally and within subnets in the the PCS network. Each subnet includes at least one BSC which controls one or more base stations for communicating with mobile stations. Each BSC is configured as an IP node on the subnet and is assigned its own IP address. Each mobile station is associated with a xe2x80x9chomexe2x80x9d subnet and assigned a permanent IP address, called the home address, which identifies the MS""s home subnet and does not change with the location of the MS in the network. When the MS is outside its home subnet, it is assigned a temporary Care Of Address (COA) as discussed in detail below. The BSCs are interconnected together and to a Gateway Router (xe2x80x9cGRxe2x80x9d) and the BSCs are configured to support IP layer functions and perform data routing based on a target MS=s IP address.
Each particular subnet in the PCS network is also provided with one or more mobility agents, preferably included within network IP routers. In a particular embodiment, two agents are used: a Home Agent (xe2x80x9cHAxe2x80x9d) and a Foreign Agent (xe2x80x9cFAxe2x80x9d). The HA implements a router function that maintains the current location of each MS in the network which calls that particular subnet home. The FA implements a router function which is used to facilitate data communication with mobile stations connected to the particular subnet but foreign to it, i.e., they call another subnet home. When an MS connects outside of its home subnet, it is considered to be in a foreign network and is assigned a temporary COA. The mobility agents use the COA to coordinate the transmission of datagrams between a foreign MS and a remote site which directs communications to the MS""s home network permanent IP address. Generally, the COA changes as the MS changes its point of attachment to the network. Preferably, mobile communication across subnets is accomplished through the Mobile IP methodology. This methodology, which was developed for use in LAN environments, defines a packet re-addressing approach that relies on agents and encapsulation to forward datagrams to the mobile host at its current location in the network.
According to the architecture of our invention, PCS registration and mobility management functions are executed using conventional mobility management flunctionality while mobility management of users accessing the Internet is based on Mobile IP architecture with additional support capabilities added to the BS-MS radio link. Advantageously, Mobile IP is flexible and can be used with any lower layer protocols. In addition, the architecture of our invention is general and maintains a strict separation between the radio subsystem and the network subsystem so that any PCS air interface technology may be used with the defined architecture. The protocols for intemetworking require no changes to the Mobile IP methodology and only minimal enhancements to existing PCS signaling systems.